There are many things that can cause your battery to fail inside your device, here's a list. You can also check out our ultimate guide to vape battery safety.
Coil resistance - using a coil whose resistance is too low will pull a current that the battery can't handle. For more information check out our mechanical mod safety resistance chart.
High Wattage - if the wattage of the battery it too high heat can trigger thermal runaway inside the battery
Exposing your mod to extreme temperature - if your mechanical mod is left in the car on a hot day or near a stove or fire in your home this heat can cause the battery to fail.
Overcharging - if the battery is overcharged the excessive voltage can increase the wattage and current to dangerous levels
Extending triggering - if the button to fire your device is held down too long the current draw can cause it to fail
Device or battery short - if there is a short in your device or a fragment of metal this will draw the current.
These are just a few of the many scenarios in which your battery could fail so it pays to be vigilant as many of these things are easily overlooked and the consequences could be deadly.